1. Field of the Invention
This invention relates to an optical switch that is used in optical communications to switch or cut off an optical path such as a fiber optic transmission path.
2. Description of the Related Art
Conventionally, mechanical optical switches designed to directly drive optical fibers or prisms to switch optical paths have been often used as optical switches for switching or cutting off fiber optic transmission paths as used in the field of optical communications. The mechanical optical switches designed to directly drive optical fibers to switch or cut off optical paths are relatively simple in structure and have features including low insertion loss, small size, and low power consumption. Therefore, many structures have been proposed. FIG. 4 shows such a structure.
This structure is a 1×2 optical switch, and is made up of a single movable raw optical fiber 1 having a base portion cantilevered to a first cylindrical tube 7, a magnetic body 5 having desired magnetic characteristics and firmly fixed to the surface of the movable raw optical fiber 1 near its front end, a hollow solenoid coil 6 for inverting the magnetic poles at the opposite ends of the magnetic body 5 by varying the sense of current flowing through the magnetic body, a pair of permanent magnets 8a, 8b for applying a magnetic attractive force to the magnetic body 5 perpendicularly to the optical axis, cylindrical halves 3a and 3b having flat portions provided with V-shaped grooves 4, two fixed raw optical fibers 2a and 2b fixed over the V-shaped grooves 4, and an elongated cylindrical sleeve 9 for holding the first cylindrical tube 7 and cylindrical halves 3a, 3b in alignment. The sleeve 9 also holds the hollow solenoid coil 6 and the permanent magnets 8a, 8b. 
The operation of the present structure is as follows. The movable raw fiber 1 is magnetically attracted to either one of the permanent magnets 8a and 8b according to the magnetic poles of the opposite ends of the magnetic body 5. The front end of the movable raw optical fiber 1 is optically coupled to either one of the two fixed raw optical fibers 2a and 2b over the V-shaped grooves 4 formed in the flat portions of the cylindrical halves 3a and 3b. The hollow solenoid coil 6 is electrically energized to apply a magnetic field to the magnetic body 5 along the optical axis. In this way, the magnetic poles of the opposite sides of the magnetic body 5 are inverted. The movable optical fiber 1 is attracted to the other permanent magnet and optically coupled to the other fixed raw optical fiber. When the solenoid coil is not electrically energized, the magnetic body 5 is also magnetically attracted to any permanent magnet. Therefore, coupling into one of the two fixed raw optical fibers 2a, 2b can be maintained. Consequently, a self-holding switching operation can be obtained.
The above-described operation pertains to 1×2 optical switching operation. If one takes notice of one optical path, this structure can also be used as an optical shutter, because it can uninterrupt and interrupt the optical path.
Besides, an optical switch designed to directly drive an optical fiber to switch an optical path has been proposed.
In the related art structure shown in FIG. 4, main components such as cylindrical halves 3a, 3b and elongated cylindrical sleeve 9 require quite high machining accuracy and assembly accuracy. For this reason, the costs of the components are high. In addition, it takes a long time to assemble the structure. In this way, high costs have been incurred.
Existing mechanical optical switches, not limited to the above-described structure, are relatively simple in construction but components machined at high accuracy are required. Even if the components are machined at higher accuracy, it takes a long time to make adjustments during assembly in order to obtain high-performance optical characteristics, because there are machining tolerances and assembly errors. Hence, they have the problem that they are not adapted for mass production and cost reductions.
In view of the foregoing, the present invention has been made. It is an object of the invention to provide a high-performance, low-cost, optical switch which is relatively simple in structure, includes main components capable of being fabricated economically and accurately, can be easily adjusted during assembly, and is adapted for mass production.